[Coco] Coco3FPGA problem at 25MHz that goes away at 1.79MHz

[Michael Furman]

I seem to have found some problem with running Nitros9 on a 25MHz Coco3 FPGA.  

When at 25MHz it seems that if I run inetd, telnet in, and run procs the output has some junk in it and then the coco3fpga board crashes.  If the CPU speed is set at 1.79MHz then this doesn't happen (at least in as many times as I can type ``procs'' in a row).  This is the only change that makes the problem go away that I know of.

The rest of this tl;dr email contains my troubleshooting steps.  Maybe someone has something else to try that I have missed:

My initial Setup that reproduced the problem:

- Raspberry Pi running Raspbian
- FTDI usb/serial adapter
- DriveWire 4.3.3c
- Coco3FPGA 20110514 build; 25 MHz; 460800 bps
- Nitros9 3.2.9 (15 Sep 2013 build date; lwtools-port)

Changes:

1) Upgrade Drivewire to 4.3.3p. Still reproduces problem.
2) Replace FTDI usb/serial with PL2303. Still reproduces problem.
3) Lower serial rate to 230400. Still reproduces problem.
4) Lower serial rate to 115200. Still reproduces problem.
5) Lower CPU Speed to 1.79 MHz.  Problem goes way.
6) Coco3FPGA 20101215 @ 25MHz.  Still reproduces problem.
7) Coco3FPGA 20101115 @ 25MHz. Still reproduces problem.
8) Nitros9 3.2.8 15 Dec 2010 build date (mamou) @ 25MHz. Still reproduces problem.
9) Replace Raspberry Pi with Mac running Drivewire 4.3.3p; FTDI Serial @ 115200; Still reproduces problem @25MHz, though it takes running procs a few more times than once or twice to get it to happen.


Here is the full repro recipe:

1) Set Coco3FPGA to 25MHz
2) Boot Nitros9 http://www.nitros9.org/latest/nos96809l2v030209coco3_becker.dsk
3) start inetd
2) telnet in
5) run procs.  When run it prints some junk on the screen mixed in with the procs output then the coco3fpga crashes.  Sometimes it takes running procs twice or a few times more than that for it to crash:

$ telnet 172.16.1.17 6809
Trying 172.16.1.17...
Connected to 172.16.1.17.
Escape character is '^]'.
DriveWire Telnet Server 4.3.3p

NitrOS-9/6809 Level 2 V3.2.9 on the Tandy Color Computer 3  2013/09/15 15:03:54


User name?: 

Process #04 logged on   2013/09/15 15:03:56
Welcome!

Welcome to NitrOS-9 Level 2!


Shell+ v2.2a 13/09/15 15:03:56

{N2|04}/DD:procs

         User                     Mem Stack
Id  PId Number  Pty Age Sts Signl Siz  Ptr   Primary Module
--- --- ------- --- --- --- ----- --- ----- ----------------
  2   1     0   128 131 $80    0   31 $79E2 Shell 
  3   2     0   128 129 $80    0   31 $76E2 inetd 
? 5 ?    0? 12 12 $8 ? 0  31? P?cs ell

                                   {?|04/D?Connection closed by foreign host.




---

Michael R. Furman
Email: n6il at ocs.net
Phone: +1 (408) 480-5865